To write a fraction as a percent, first remember that a percent is a ratio of a number to 100. If we want to convert
to a percent, we need to find a fraction equivalent to
that has a 100 in the denominator. We can do this by setting up a proportion.
=

Now, we can use cross products to find the missing value.
3 × 100 = 300
20 × n = 20n
300 = 20n ← Divide both sides by 20.
15 = n
Therefore,
as a percent would be 15%.